A silder crank mechanism is shown in fig: Let the crank OB makes an angle θ with the inner dead centre (IDC) and rotates in a clockwise direction about the fixed point O with uniform angular velocity ω_{BO} rad/s.

∴ Velocity of B with respect to O or velocity of B,

v_{BO} = v_{B} x ω_{BO} OB, acting tangentially at B.

We know that centripetal or radial acceleration of B with respect to O or acceleration of B,

a^{r}_{BO} = a^{B} = ω^{2}_{BO} x OB = v^{2}_{BO}/OB